Volume 13, Number 9—September 2007
Spectrum of Infection and Risk Factors for Human Monkeypox, United States, 2003
|Study classification||Classification by case definition†||Criteria met
|Probable||Yes||Yes (fever with vesicular pustular rash, or rash of unspecified type plus IgM)||No (if rash type unspecified, IgM 7–56 d after rash onset)|
|Not included||Suspect||Yes||No (fever or rash of unspecified type)||No|
|Control**||Not a case||Yes||No||No|
|Infected but not diseased||Unclassified||Yes||No||No (IgM detected at time of study)|
*IgM, immunoglobulin M.
†Available from www.cdc.gov/ncidod/monkeypox/casedefinition.htm, January 2004 (3,12,13).
‡Epidemiologic criteria for classification of monkeypox cases included exposure to an exotic or wild mammalian pet (obtained on or after the known importation event) exhibiting signs of illness (e.g., conjunctivitis, respiratory symptoms, and rash); exposure to an exotic or wild mammalian pet that had been exposed to an animal infected with monkeypox; or exposure to a suspected, probable, or confirmed human case of monkeypox.
§Clinical criteria were rash (macular, papular, vesicular, or pustular; generalized or localized; discrete or confluent) plus fever (subjective or measured temperature >99.3°F [>37.4°C]), plus >2 other signs and symptoms (chills and/or sweats, headache, backache, lymphadenopathy, sore throat, cough, shortness of breath), all beginning <21 d after last possible exposure.
¶Laboratory criteria included culture of monkeypox virus, or demonstration of monkeypox virus DNA by PCR from patient clinical specimens, or demonstration of virus morphologically consistent with an orthopoxvirus by electron microscopy or immunohistochemical testing methods (in the absence of exposure to another orthopoxvirus).
#Positive laboratory findings were sufficient to confirm a monkeypox case in the absence of complete clinical or epidemiologic history.
**Persons investigated but ruled out as having monkeypox virus infections were eligible to enroll in the study as controls; additional controls were identified as in Patients and Methods.